The present invention is in the field of high frequency medical X-ray generators. More particularly, the invention is directed to improvements in high frequency X-ray generators for the radiographic or medical imaging applications, or so-called diagnostic X-ray equipment. More particularly yet, the invention concerns a milliamp-seconds (MAS) regulator circuit for a high frequency medical X-ray generator.
The invention is directed to a novel and improved milliamp-seconds (MAS) regulator circuit which produces a control signal which may be utilized to stop the X-ray exposure when the milliamp-seconds delivered by the X-ray tube becomes equal to or greater than some predetermined desired amount set by the operator on a control console or the like.
While the comparison of actual X-ray tube MAS to desired MAS has heretofore been utilized for control purposes, our novel and improved system determines the actual MAS in a novel fashion by what will be referred to herein as "digital integration". Moreover, our novel and improved system utilizes a highly reliable digital method of signal processing and comparison for developing a control signal for stopping the exposure in accordance with the actual and desired MAS values.
Advantageously, the use of modern digital circuit components and digital logic-type controls make possible increased accuracy and reliability of the operation and control of the X-ray generator. Moreover, the use of digital control logic also makes possible the addition of further control logic in the MAS regulator circuit arrangement for achieving additional advantageous and desirable control functions. In the preferred embodiment illustrated herein, these further logic controlled functions include inhibiting the operation of the MAS regular circuit when the X-ray tube kilovoltage (KV) is less than 75% of the selected or desired value. Such additional logic control signals may also be utilized to inhibit the operation of the MAS regulator circuit until a digital logic "ready" or "prepared" signal is produced indicating that the generator is prepared to make an exposure.
Briefly, in accordance with the foregoing considerations, a novel and improved MAS regulator system in accordance with the invention comprises first converter circuit means for converting a signal corresponding to a desired MAS value into a first digital signal of a given format; digital integrator circuit means for integrating and converting the actual MA current in the X-ray tube to a digital MAS signal corresponding to the actual MAS value of the current in the X-ray tube, said MAS signal being in the form of a second digital signal of the same predetermined format as said first digital signal; and comparing circuit means for comparing said first and second digital signals and for producing a control signal to stop the exposure when the second digital signal is greater than the first digital signal.